We don't really have weak units, partially because everything we have is currently good at one of three things:
Having a good defense/armor value (Metal Legion, Mehal Saefari)
Has a good utility (Bath cav, crow runners)
Can Maneuver like a bat out of hell (Bath Cav, Lord of Steel)
If anything, the Dreadnought and Crow Runners are probably the weakest overall, simply because they tend to be more middle-of-the-road than the others.